rear main seal?

[jim325]

So, I got what I am pretty sure is engine oil leak near the back of the engine. I initially figured it was a rear main seal. So I pulled the motor but I am not entierly sure it is a rear main seal...

I just rebuilt the motor, all new seals and gaskets, bearing, yada yada yada. I will get some pictures but there isint obvious damage to the rear main seal. The oil was dripping onto my exhaust so it had to have either been coming from pretty high up or slinging around in good shape. The duck gasket was replaced and the head thoroughly cleaned. It doesn't look like the oil is coming from there.

I had the motor running after the rebuild, sounded great. No lower end noise and prolly coulda used a slight valve adjustment but if you stood 10 feet away you couldn't hear any noise from the head(thinking M20 typerwriter as I have never really heard a normal running M30)

I'm gonna take the rear main seal cover off tomorrow and check the gasket behind it, the seal, and the oil pan but if I don't find anything obvious how am I gonna know what it is? Or should I just rereplace it all and hope for the best?

I'll double check the crankshaft endplay but I am pretty sure it was nice n tight after the rebuild.

Pretty burnt out about having the car running and ready for the road other than a radiator fan to see oil steadily dripping from the right side

Motor is in an e30, which is one reason I didn't just pull the transmission to look at the rear main.

[Bimmerguy2002]

is your brake fluid reservoir low?

[jim325]

Nope, just as full as can be. So is the transmission.

[m535is]

Are you sure the head gasket is not leaking? They do leak oil externally and where you are talking about sounds close to one of the normal places.

[slammin_e28]

Motor is in an e30, which is one reason I didn't just pull the transmission to look at the rear main.

I am confused now. You list M30, M20, then an '80 3 series.

If it's an M20, check the back of the head. The half moons like to leak. HG also with high miles.

...but I'm guessing you have an M30 'cause I'm M30 biased.

Personally, I'd clean everything up real nice (back of the engine and under car where engine->trans, etc) and drive it, then inspect for leaks, and trace back.

[jim325]

Ok, ill try to be more specific on engine and vehicle. And to clarify, I only said M20 to relate the top end "clatter" as im guessing a properly adjusted M30 will make somewhat of the same noise as a properly adjusted M20, but I have never actually heard an M30 running before. Other than this motor.

The engine is from an 86 535i manual transmission.
The body is an 89 325i.

The engine is now turbo, goodntight maniofold, PF MS ECU.

The headgasket is a new MLS gasket with ARP headstuds torqued to 40, 60, 80 if I remember correctly. I'd have to double check to be 100% sure on torque.


I took the transmission off the engine before work today. The rear main seal looks ok, not damadged. I am pretty sure I installed it correctly. It's set back in the cover about about 1/8 an inch or so. Didn't get the seal plate off but I will after work to check the condition of the gasket.

It could possibly be the head gasket I suppose which would explain it running down the right side of the motor.

My clutch disk is a a little wet, not real sure if it is water or oil. Didn't really look to hard at it yet. The block plug in the rear is new and doesn't appear to be the problem.

I just can't imagine if it was the rear main seal why it wouldn't come out the left side of the bellhousing first. There are holes over there for some sensors or something that arent being used, maybe flywheel sensor of some sort? Since the engine spins clockwise(looking from rear of motor towards front) would it hit the flywheel and likley sling over there than drip more than the right side?

Regardless im going to take a few more pieces off the back, check gaskets and gasket surfaces and look for any cracks, cuts, unlevel surfaces and what not.

[m535is]

My only experience with an MLS head gasket on an M30 was really poor. I had oil leaking out of it on the passenger side even though I had the block and head surfaced to use the MLS. I ended up replacing it with a BMW unit and it fixed the problem. I honestly am not sold on MLS head gaskets for these older cars. If you have oil down the right side of the block, especially higher up, then it is the head gasket.

[jim325]

Well. When I get home today I am going to reinstall the motor minus the transmission. Start it up and let it run till I see oil leaking. That should make it more than easy to see where the oil is coming from.

[alpinacsi]

One of the bolts on the cover with the duck gasket has a washer with a rubber seal: was this seal installed in the correct location? Also make sure the oil pressure sender is not leaking and working it's way around the back of the head. The sender itself can leak and not where it screws into the head.

[jim325]

I did check the duck gasket the other day. There was a bolt with a rubber oring on it but im not sure if it's in the right spot. I got no idea where it's exact location is.

I'm not using a regular oil pressure sensor. I'm using a T there to goto my mechanical oil pressure gauge and to my turbo. That hose to my mechanical gauge is a suspect part tho but it will be much easier to see with no transmission attached. I did put a new copper seal between the head and the fitting.

[jim325]

Im a little confused as to which brand of headgasket would be the best to replace my MLS.

Should I go with Victor Reinz, Elring Klinger, or the one from Pelican that says Genuine BMW?

I don't want to buy a felpro headgasket, im not even sure they sell one for the m30b34 but im not gonna try n find out.

Thanks.